Get char array from byte array and then back to byte array

Question

I don't know why but when you do the next thing you will never get the same as the original byte array:

var b = new byte[] {252, 2, 56, 8, 9};
var g = System.Text.Encoding.ASCII.GetChars(b);
var f = System.Text.Encoding.ASCII.GetBytes(g);

If you will run this code you will see that b != f, Why?! Is there any way to convert bytes to chars and then back to bytes and get the same as the original byte array?

Because `252` can't be be used as ASCII char(it is 7 bit). So converting between any arbitrary byte array and string can be lossy. — L.B, Mar 01 '14 at 18:57
@ZilbermanRafael use `Convert.ToBase64String` and `Convert.FromBase64String` — L.B, Mar 01 '14 at 18:59
@ZilbermanRafael Yes convert the algorithm(or data) into smaller steps that can be run in parallel and use a super computer. http://en.wikipedia.org/wiki/General-purpose_computing_on_graphics_processing_units — L.B, Mar 01 '14 at 19:05
The fastest way to convert `byte[]` to something back to `byte[]` is clearly identity transformation :). If you can specify your exact requirement there could be some other way... (also Base64 is quite standard and easy to implement if you need to deal with huge arrays) — Alexei Levenkov, Mar 01 '14 at 19:05
@ZilbermanRafael Yes, it matters because it might be that you do not need to go via chars. — Andrew Morton, Mar 01 '14 at 19:08
@ZilbermanRafael,if you want TABLE ASCII -II in encoding for value between 128 to 255, may be you can read my latest post. thanks — V-SHY, Mar 01 '14 at 20:10

score 3 · Accepted Answer · edited May 23 '17 at 12:10

byte value can be 0 to 255.

When the byte value > 127, then result of

System.Text.Encoding.ASCII.GetChars()

is always '?' which has value 63

Therefore,

System.Text.Encoding.ASCII.GetBytes()

result always get 63 (wrong value) for those have initial byte value > 127

If you need TABLE ASCII -II then you can do as following

        var b = new byte[] { 252, 2, 56, 8, 9 };
        //another encoding
        var e = Encoding.GetEncoding("437");
        //252 inside the mentioned table is ⁿ and now you have it
        var g = e.GetString(b);
        //now you can get the byte value 252
        var f = e.GetBytes(g);

Similar posts you can read

How to convert the byte 255 to a signed char in C#

How can I convert extended ascii to a System.String?

score 0 · Answer 2 · answered Mar 01 '14 at 20:52

Why not use chars?

var b = new byte[] {252, 2, 56, 8, 9};
var g = new char[b.Length];
var f = new byte[g.Length]; // can also be b.Length, doens't really matter
for (int i = 0; i < b.Length; i++)
{
   g[i] = Convert.ToChar(b[i]);
}
for (int i = 0; i < f.Length; i++)
{
   f[i] = Convert.ToByte(g[i]);
}

score -2 · Answer 3 · answered Mar 01 '14 at 19:15

-2

The only difference is first byte: 252. Because ascii char is 1-byte signed char and it's value range is -128 to 127. Actually your input is incorrect. signed char can't be 252.

answered Mar 01 '14 at 19:15

Mustafa Chelik

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I wasn't talking about actual ascii. I was talking about ascii in the code. I wrote purposely this way to be easy to understand. I know there is nothing called ascii unsigned char. – Mustafa Chelik Mar 01 '14 at 19:25
in c, refer answer @Adrian McCarthy, http://stackoverflow.com/questions/13161199/ascii-table-negative-value There is no such thing as a "negative ASCII" value. ASCII defines character and control codes for values from 0 to 127. therefore your answer has problem on **signed** char – V-SHY Apr 22 '14 at 01:21

Get char array from byte array and then back to byte array

3 Answers3